Drooling is a particularly troublesome symptom in PD. The Dutch group recently published a nice study showing that it occurs in about a 1/3 of PD patients, usually later in the disease and usually associated with a mouth open appearance.

A few tricks we have used in our clinic to treat it over the years:
1- make sure sinemet is at a high enough dose and dose as well as interval is optimized
2- atropine drops in the mouth
3- Botulinum Toxin injections into the salivary glands
4- Gum chewing or candy sucking (with good oral hygiene)

J Neurol. 2011 Jun 23. [Epub ahead of print]
Diurnal and nocturnal drooling in Parkinson's disease.
Kalf JG, Bloem BR, Munneke M.
Source
Nijmegen Centre for Evidence Based Practice, Department of Rehabilitation, Radboud University Nijmegen Medical Centre, Internal code 897, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands, h.kalf@reval.umcn.nl.
Abstract
Drooling as symptom of Parkinson's disease (PD) has thus far been poorly defined. This uncertainty is reflected by high variations in published prevalence rates. The aim of this study was to investigate the prevalence of saliva loss versus accumulation of saliva as a possible preliminary stage, and diurnal drooling versus nocturnal drooling. In addition, we evaluated the association between drooling severity and the severity of facial and oral motor disorders. We collected age, disease duration, UPDRS III and Hoehn & Yahr stage from 104 consecutive outpatients with PD. Diurnal and nocturnal drooling was evaluated with a validated questionnaire (ROMP-saliva). A speech pathologist, blinded for drooling severity, rated facial expression, involuntary mouth opening and difficulty with nose breathing and also interviewed patients about sleeping position and nose-breathing during the night. Thirty patients (29%) had no complaints with saliva control ('non-droolers'), 45 patients (43%) experienced accumulation of saliva or only nocturnal drooling ('pre-droolers'), and 29 (28%) had diurnal drooling (24 of which also drooled during the night; 'droolers'). The droolers had longer disease duration (10 vs. 7 years, p = 0.01) and drooling was independently associated with involuntary mouth opening (OR = 2.0; 95% CI 1.02-3.99) and swallowing complaints (OR = 1.2; 95% CI 1.03-1.31). Diurnal drooling-defined as dribbling of saliva while awake-is present in about 28% of PD patients. This is less than usually reported. Diurnal drooling typically appeared later in the disease course. The association with oral motor behavior should encourage the development of behavioral treatment approaches.

My saliva is pooling in my mouth during sleep & I awaken suddenly unable to breathe. I cough up almost a tennis ball size of clear secretions.The ball stays intact in the toilet. It's pretty scary. I've tried GERD meds, elevating the bed frame, scopace. I was treated for mycobacterium avium complex with 1 year antibiotics 2009-2010. I am 3 years post DBS, increasing difficulty with speech, 2 normal swallow studies (last one was 2 years ago). Coughing a lot during the day. I've read some blogs online that talk about using pineapple juice, papaya or vinegar to help with the saliva issue. Some say it is because of infrequent/inadequate swallowing so the saliva thickens & pools. Any thoughts or studies out there?

Not sure about what you have suggested.....however we have tried botox for drooling with great success. Some docs use benadryl at bedtime to control the drooling but watch out for side effects such as cognitive issues.